Todd,
Its not really the detritus that creates the nitrate, but the very efficient wet/dry filtration. They convert the ammonia to nitrite and then to nitrates, which is their job. And they do it well.
Its best used in systems with not much or limited live rock or in stores, etc. where large increases in bio loads needs to be handled. Live rock & sand beds provide all the bio capability one needs in a normal fish only or reef tank. Both the sand bed & oxygen starved areas, {which bio balls dont have}, of the live rock, provide a place where denitrification bacteria can thrive.
The use of rubble in a sump can contribute to detritus, which in turn helps promote phosphates & nitrates. Most use it in a refugium, that receives cleaner, filtered water, so the accumulation is less.
I do know of aquarists with not much live rock and they use some type of wet/dry filter. They also use a sand bed or algaes in a sump to help with nitrate removal. Some also employ the sulphur reactors for that purpose.
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Doug
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